During the past several years electrical timepieces have become increasingly popular with the result that numerous types and styles have been developed. In many of the present day timepieces the basic determination of frequency is by means of a high frequency crystal resonator controlling an oscillator. The output of the oscillator is passed through a frequency divider to produce a sequence of pulses of low frequency suitable for driving a display arrangement. Such display arrangements may either employ time indicating hands or comprise a digital display which in turn may employ a passive material or an active material.
In general, the pulse output from the final stage of the frequency divider is such as to apply one pulse each second to the display. Where a classic type of display is used the pulse sequence controls a stepping motor and through the stepping motor a series of gears whereby seconds, minutes, hours and eventually the date may be displayed. In the case of digital timepieces further registers are required and the frequency of the output is further divided in order to provide signals corresponding to seconds, minutes, hours and, where desired, the date. The outputs of these various registers are finally transmitted to a decoding arrangement whereby the display may finally be activated by the decoded signals.
In all of these various types of electronic timepieces a persistent problem arises when it comes to setting and correcting time as displayed. Moreover, since such timepieces are generally reputed to have a very high degree of precision it becomes intolerable to the user thereof that the time as displayed should show discrepancies with official time signals. Thus, means must be provided permitting easy corrections and alterations of the display. For instance, where the owner of the watch may cross time zones it is desirable to be able to reset the hour display without in any way disturbing the remaining displays. Finally, even where one is primarily concerned with timepieces of the electromechanical type it is desirable, where possible, to replace strictly mechanical arrangements for timesetting and correcting by suitable electric circuits which, in general, are easier to implement and may in the long run turn out to be more reliable.
In British specification No. 1,399,024 there has been described an electronic correction circuit for use in timepieces which permits easy correction of the seconds display. This is effected by means of a push-button which for each activation thereof adds one second to the display. Should, however, the user wish to remove or in effect, subtract seconds in the case where the time displayed is in advance of the correct time, the same push-button is maintained depressed over a predetermined period of time and whereas the initial impulse given thereby adds one second to the display, thereafter the display is stopped for as long as the push-button is maintained depressed.
This arrangement, although useful, provides only mechanical means for general time setting. A subsequent proposal was therefore set forth in British specification No. 1,434,443 in which a switching circuit was provided to enable the user by activation thereof to switch a much higher frequency from the divider circuit to the display, whereby the minutes display would be advanced at a very much higher rate. In that specification, moreover, there was described a mechanism for correcting the hour hand (and calendar if provided), without disturbing the other portions of the display. No arrangement was shown for correction of seconds.